Collateral grading system for analysis of the collateral map
| Score | Description of Collateral Status |
|---|---|
| 5 (Excellent) | No or smalla collateral-perfusion delay in the MCA territory in the capillary phase regardless of the collateral status in the arterial phase |
| 4 (Good) | Collateral-perfusion delay equal to or less than one-half of MCA territory in the capillary phase and no or small delay in the early venous phase |
| 3 (Intermediate to good) | 1) Collateral-perfusion delay equal to or less than one-half of the MCA territory in the capillary phase and equal or less than one-half in the early venous phase |
| 2) Collateral-perfusion delay more than one-half of the MCA territory in the capillary phase and no or small delay in the early venous phase | |
| 2 (Intermediate to poor) | Collateral-perfusion delay more than one-half of the MCA territory in the capillary phase and equal to or less than one-half in the early venous phase |
| 1 (Poor) | Collateral-perfusion delay more than one-half of the MCA territory in the early venous phase and equal to or less than one-half in the late venous phase |
| 0 (Very poor) | Collateral-perfusion delay/defect more than one-half of the MCA territory in the late venous phase regardless of perfusion status at previous phases |
↵a “Small” indicates an area <1 of 8 MCA regions (Fig 5).